1. Field Of The Invention
This invention relates to a new and improved cover and method of making such covers for molten metal and slag runners as are used in the steel and other industries for delivering molten metal from a source such as a blast furnace to a remote point.
2. Description Of The Prior Art
In steel-making, a blast furnace puts out molten metal together with slag floating atop it. This hot flowing material is caused to run down troughs, called "runners", some of which are for the combination and some of which are for slag separated from the metal and others of which are for the molten metal itself.
For many years, such runners were simply left open and gas, heat and particles were allowed to emit in large quantities into the atmosphere. Lately, however, in response to environmental concerns, governmental regulations, and a desire to conserve energy, some of these runners in some plants have been covered, usually as a retro-fit operation.
Various suggestions for covered runner systems are described in U.S. Pat. Nos. 4,355,788; 4,357,003; 4,300,753; and 4,354,668.
Those steel mills using covers have, however, run into problems among which is the tendency of the covers to warp, thus, opening gaps which release gas, heat and particles. Such prior art covers have tended to be expensive to make and use. Furthermore, the life of these covers has been relatively short, requiring frequent replacement with a resulting high cost.
Past commercial covers have used relatively heavy weight sheet metal backing into which a layer of ceramic insulating material (facing inward toward the molten metal and slag) is formed.